KR20060108688A - Refractory alloy and mineral wool production method - Google Patents

Abstract

The invention relates to an alloy having high temperature mechanical strength in an oxidising medium and comprising a carbide-precipitation-strengthened matrix containing chromium. The invention is characterised in that the alloy comprises carbides of at least one metal (M) selected from among titanium, zirconium and hafnium, said carbides also optionally containing (M') tantalum. The invention is suitable for articles that require high temperature mechanical strength, such as for hot glass processing or production.

Description

REFRACTORY ALLOY AND MINERAL WOOL PRODUCTION METHOD}

FIELD OF THE INVENTION The present invention relates to metal alloys for use at very high temperatures, in particular a process for fiberizing a molten mineral composition to produce a mineral wool, but more generally a high mechanical strength in an oxidizing environment such as molten glass. A metal alloy that can be used in a process for producing a tool having a metal alloy, and the glass or any other such as cobalt-based alloys that can be used at high temperatures, in particular components of machines for producing mineral wool. To alloys for producing articles for hot smelting and / or conversion of mineral substances.

One fiberization technique, called an internal centrifugation process, is that liquid glass is continuously dropped into an assembly of axisymmetric parts that rotate at a very high rotational speed about its vertical axis. One main part, called a "spinner", receives glass from a wall called a "band", which is perforated, through which the glass flows through the centrifugal force, from all its parts in the form of molten filaments. Come out. An annular burner located above the outside of the spinner, which creates a descending stream of gas along the outer wall of the band, deflects this filament downward. This filament is then "solidified" in the form of glass wool.

Spinners are thermally (thermal shock during start-up and shutdown procedures, temperature gradients along parts during constant use), mechanically (centrifugal force and corrosion due to flow of glass), chemically (melted glass, spinner circumference) Oxidation and corrosion caused by hot gases emitted by the burner.) The main method of deterioration of spinners is hot creep deformation of vertical walls, the appearance of horizontal or vertical cracks, and the corrosive wear of fibrous orifices which very simply requires component replacement. Thus, the constituent material must be able to withstand a long enough manufacturing time to conform to the technical and economic constraints of the process. For this purpose, materials are found that have specific ductility, creep resistance and corrosion and / or oxidation resistance.

Many of the materials known for making such tools are superalloys based on nickel or cobalt based on the hardening of carbides. In particular, refractory alloys are based on chromium and cobalt, which are refractory elements that provide improved high temperature intrinsic mechanical strength to the alloy's matrix.

Thus, WO-A-99 / 16919 describes an alloy based on cobalt which has improved high temperature mechanical properties and essentially comprises the following elements (in weight percent of the alloy).

Cr 26 to 34%

Ni 6-12%

W 4-8%

Ta 2-4%

C 0.2-0.5%

Less than 3% Fe

Si less than 1%

Mn less than 0.5%

Zr less than 0.1%

The remainder consists of cobalt and inevitable impurities, with a tantalum / carbon molar ratio of about 0.4 to 1.

The choice of carbon and tantalum content is intended to form in the alloy a dense but discontinuous intergranular carbide network {required composition of chromium carbide and tantalum carbide TaC in the form of Cr ₇ C ₃ and (Cr, W) ₂₃ C ₆ }. . This choice provides the alloy with improved high temperature mechanical and oxidation resistance properties, allowing the molten glass with a temperature of 1080 ° C. to be fiberized.

WO 01/90429 discloses cobalt-based alloys which can be used at higher temperatures than this, which have a fine structure of at least 1100 ° C., advantageously 1150 ° C., due to the microstructure in which the intergranular region is rich in tantalum carbide precipitates. In the above, an excellent compromise between mechanical strength and oxidation resistance is provided. On the one hand, these carbides act as mechanical reinforcing agents that resist intergranular creep at very high temperatures, and on the other hand, these carbides oxidize due to oxidation to Ta ₂ O ₅ , which affects the previous volume of TaC carbides. It forms a fully filling oxide to prevent aggressive media (liquid glass, hot gases) from penetrating into the interparticle space. The following sufficient amounts of tantalum carbide are provided.

A suitable carbon content (based on the weight of the alloy) combined with a sufficiently high tantalum content (Ta / C molar ratio of at least 0.9 and preferably from about 1 to 1.2) suitable for damaging all other carbides to improve the formation of TaC carbides , About 0.3 to 0.55%, preferably about 0.35 to 0.5%),

Or a relatively high carbon content (about 0.8 to 1.2%, preferably about 0.9 to 1.1%) combined with the tantalum content such that the tantalum to carbon molar ratio (Ta / C) of less than 0.9 can be as low as 0.3, preferably 0.35 Tantalum carbide is provided. The microstructure then has a very dense network of intergranular carbides comprising M ₂₃ C ₆ carbides, which tend to dissolve into solid solutions at high temperatures above 1150 ° C., leaving only TaC at the crystal boundaries.

In one embodiment, an alloy is used under industrial conditions for fiberizing glass at a temperature of about 1200 to 1240 ° C. of the fiberizing spinner. This means that the temperature of the metal along the profile of the spinner is 1160 to 1210 ° C. The life of the spinner reaches 390 hours.

Especially in industrial production for fiberizing basalt glass, however, in order to have greater flexibility in controlling production conditions, it seems desirable to provide mechanical strength over a metal temperature range of 1200 ° C. or higher.

It is an object of the present invention to provide a further improved alloy that has a higher mechanical strength at high temperatures, allowing operation at metal temperatures of 1200 ° C. or higher.

In this respect, the subject matter of the present invention is an alloy comprising a chromium containing matrix which has high mechanical strength at high temperature in the oxidation medium, is free of molybdenum and / or tungsten and is reinforced by precipitation of carbides,

The alloy is characterized in that it comprises a carbide of at least one metal (M) selected from titanium, zirconium and hafnium, said carbide optionally further comprising tantalum (M '). The expression “without Mo and / or W” means, for the purposes of the present invention, that the weight percent content of each of these two elements in the alloy is less than 1%, generally less than 0.1%, and more specifically these two elements. Each is understood to mean that it is present in the form of undesirable impurities.

In particular, the present invention relies on the finding that carbides of metals other than tantalum have a very satisfactory strengthening effect and can be used as a complete or partial replacement of tantalum carbide, in particular to improve the high temperature performance of refractory alloys.

Such carbides of the metal (M) selected according to the invention are characterized by durability during prolonged exposure to high temperatures (for hundreds of hours), while tantalum carbides under the same exposure conditions undergo decomposition, and such decomposition leads to reinforcement of the material. Disperse and make it coarse. Some of these carbides, the first "hooked" typical forms, employ spherical geometries that correspond to the thermodynamically most stable state that minimizes carbide / matrix interfacial energy. This degradation is accompanied by partial decomposition of carbides in the matrix.

As described in WO 01/90429, mechanical strength is a major factor in the life of the spinner for high fiberization temperatures of 1150 to 1200 ° C. and above. Thus, the resistance at this temperature of the strengthening precipitate is critical to determining the life of the material.

Zirconium, hafnium and titanium carbides offer very large improvements in terms of high mechanical strength.

Surprisingly, the inventors of the present invention find that mixed carbides containing tantalum in addition to other metals (M) in Ti, Hf and Zr contain more than carbides containing only tantalum and only other metals when the other metal is Ti or Zr. It has also been found to be much more temperature stable than carbides. The expression "stability at high temperature" is understood herein to mean the maintenance of carbide forms of the general "script" structure. This embodiment constitutes one particularly most preferred variant of the invention, since the alloy produced therefrom also exhibits excellent oxidation resistance.

However, hafnium carbide (HfC) is much more stable than other carbides (MC) and more stable than carbides {(Ta, M) C}. This embodiment is also advantageous.

These mixed carbides have improved high temperature microstructure-less decomposition and less coarseness of (Ta, M) C carbides. Better, the addition of Ti to TaC carbides is such that the fine secondary (Ta, Ti) C carbides, which are very useful for creep resistance in particles, spontaneously settle in the matrix (the secondary precipitates obtained by special heat treatment are generally the same. Conditions tend to vanish under conditions) while stabilizing TaC carbide at high temperatures. This high temperature stability makes these (Ta, Ti) C carbides particularly advantageous, although these (Ta, Ti) C carbides have a slightly different form than MC carbides.

The atomic content of carbon maintains the ratio of the atomic content of the metal (or sum of metals), which can be close to but greater than 1, in particular about 0.9 to 2, so that MC or (Ta) is the only hardening phase. It is advantageous to prefer, M) C carbides. In particular, in the sense that some additional carbides (chromium carbides) that can be produced do not impair the set of properties at all temperatures, a slight difference of less than one remains acceptable. Advantageous ratios range from 0.9 to 1.5.

The amount of MC or (Ta, M) C carbides should be sufficient for good high temperature mechanical action. In order to achieve this, the carbon content (which is therefore related to the content of the metal) should be very large, for example as high as 0.6% by weight. However, the carbon content can be as low as 0.2% while maintaining a good portion of the high temperature mechanical strength potential.

Preferred alloys according to the invention have a matrix based on cobalt or nickel or iron-nickel. Particular preference is given to cobalt based matrices which ensure both sufficiently high solidus temperatures and good high temperature oxidation. In such alloys, the microstructure is formed from eutectic biphasic (Co matrix / carbide) compounds present in the space between the dendritic matrix of cobalt and the dendritic crystallized in a face-centered cubic lattice. The form of these eutectic compounds consists of an intimate entanglement of carbide and matrix. The very good interparticle adhesion provided by these eutectic compounds is very advantageous for very good mechanical strength at very high temperatures.

In particular, the subject matter of the present invention is an alloy based on cobalt, which also contains chromium, nickel and carbon and is essentially composed of the following elements (the ratios are expressed in weight percent in the alloy).

Cr 23 to 34%

Ni 6-12%

M = Zr, Hf or Ti 0.2-7%

M '= Ta 0-7%

C 0.2-1.2%

Less than 3% Fe

Si less than 1%

Mn less than 0.5%

The remainder consists of cobalt and inevitable impurities.

Chromium is also present in the form of carbides of essentially Cr ₂₃ C ₆ type, in which it is partially present in the solid solution and in some cases finely dispersed in the particles (in this case, the carbides provide creep resistance in the particles), Present in the form of carbides of type Cr ₇ C ₃ or Cr ₂₃ C ₆ present at the grain boundaries (the carbides prevent the particles from slipping through each other), contributing to the intrinsic mechanical strength of the matrix, and thus also between the grains of the alloy Contribute to reinforcement Chromium also contributes to corrosion resistance as a precursor to chromium oxide, which forms a protective layer on surfaces exposed to oxidation media. A minimum amount of chromium is needed to form and maintain this protective layer. However, too high chromium content is detrimental to both toughness and mechanical strength at high temperatures because too high chromium content results in too low ductility and too high stiffness under stress, both of which are not suitable for high temperature constraints. .

In general, the chromium content of the alloys according to the invention which can be used will be from 23 to 34% by weight, preferably from about 26 to 32% by weight and advantageously from about 28 to 30% by weight.

Nickel present in the alloy in the form of a solid solution as an element to stabilize the crystalline cobalt structure is used in the general range of about 6 to 12% by weight, advantageously 8 to 10% by weight.

Carbon is an essential component of the alloy needed to form metal carbide precipitates.

The carbon content directly determines the amount of carbide present in the alloy. The carbon content is at least 0.2% to obtain the desired minimum reinforcement, but is limited to 1.2% or less to prevent the alloy from becoming hard and difficult to process due to the excessively high density of the reinforcement. The lack of ductility of the alloy at this content ensures that the imparted strain (eg of thermal cause) is not provided without breakage and that such strain is not sufficiently resistant to crack propagation.

Selected carbide forming elements according to the invention have the advantages described below.

Because titanium is a more standard and less expensive element than tantalum, it has less adverse effect on the cost of the alloy than tantalum in known alloys. It may also be advantageous that this element is a light element.

A minimum amount of titanium of 0.2 to 5% by weight in the alloy appears to be desirable for producing a sufficient amount of TiC carbide, apparently due to the solubility of titanium in the fcc cobalt matrix. A titanium content of about 0.5-4%, in particular 0.6-3%, appears to be advantageous.

Zirconium and hafnium provide excellent fire resistance with cobalt based alloys enhanced by ZrC or HfC eutectic carbides with solidus temperatures that can be 1300 ° C or higher. Zirconium and hafnium also have more limited decomposition / sparing phenomena in these carbides than impair the mechanical properties of alloys reinforced by TaC carbides, and for decades or even hundreds of hours, high temperatures, even temperatures like 1300 ° C. Has very good stability.

The amount of zirconium in the alloy may be 0.2 to 5%, advantageously 0.4 to 3%, in particular 0.5 to 1.5%.

Hafnium appears to be a very powerful carbide forming element, which produces a denser carbide network than tantalum, for the same atomic content. This is apparently due to the fact that the production enthalpy of HfC carbides is lower. Thus it is formed in greater amounts, and hafnium is also absent at all in the composition of the matrix.

The hafnium may be in an amount of 0.2 to 7%, preferably about 0.2 to 5%, especially 0.4 to 5%, especially about 1.5 to 4.5%.

HfC carbides are very stable and do not change even after long time exposure (more than 100 hours) at 1200 ° C-no decomposition or dissolution is observed in the matrix.

In order to have acceptable microstructures in alloys reinforced with HfC carbides, it appears that the Hf / C ratio is less than 1, or in some cases close to 0.5. The same explanation can be made for the oxidation resistance.

Another major advantage of this alloy is its fire resistance, so that the increase for TaC reinforced alloys can be up to 40 ° C. for the onset of melting of the alloy.

As described above, the mixed carbide in which tantalum is substituted by Zr or Ti shows improved high temperature stability, and the mixed carbide in which Ta is replaced by Hf shows excellent high temperature stability.

Tantalum, which is selectively present in the alloy, is partly in the solid solution state of the cobalt matrix, and these heavy atoms distort the local crystal lattice and hinder the movement of the displacement when the material is subjected to mechanical loading, and even block the matrix Will contribute to the intrinsic strength of. The minimum tantalum content that allows the formation of mixed carbides with the metal (M) according to the invention is about 0.5%, preferably about 1%, very preferably about 1.5%, or even 2%. The upper limit of the tantalum content may be selected to about 7%. The tantalum content is preferably about 2 to 6%, in particular 1.5 to 5%. The tantalum content is very preferably less than 5%, or 4.5% or even less than 4%. Small amounts of tantalum have two advantages. In other words, it substantially reduces the overall cost of the alloy and makes it easier to process the alloy. The higher the tantalum content, the harder the alloy is, the more difficult the molding is.

If the alloy contains tantalum and zirconium at the same time, it is desirable to keep the zirconium content very low so that zirconium acts as a substitute for a small portion of tantalum.

The alloy may contain other common constituent elements or consequent impurities. Generally, alloys are

Silicon in an amount of less than 1% by weight, which is an antioxidant of molten metal during smelting and casting of the alloy,

Manganese in an amount of less than 0.5% by weight, which is also an antioxidant;

Iron, which may be up to 3% by weight without compromising the properties of the material,

Cumulative amounts of other elements introduced advantageously as impurities ("essential impurities") having the necessary constituents of the alloy, accounting for less than 1% by weight of the alloy composition.

Include.

The alloy according to the invention is preferably free of Ce, La, B, Y, Dy, Re and other rare earth elements.

Alloys which contain very reactive elements and which can be used according to the invention can be formed by casting, in particular by induction melting and sand mold casting in an inert atmosphere.

Following casting, optionally, heat treatment may take place at temperatures that may be above the fiberization temperature.

The subject of the invention is also a process for producing an article by casting using the above-described alloy which is the subject of the invention.

This process may comprise at least one cooling step after casting and / or after heat treatment or during heat treatment, for example by air cooling, in particular to return to room temperature.

This process may further comprise a forging step after casting.

The alloy according to the invention can be used to produce all kinds of parts which are required to be mechanically stressed at high temperatures and / or to operate in oxidation or corrosion media. The subject of the invention is also such an article made from the alloy according to the invention, in particular via casting.

Among these uses, in particular, the manufacture of fibrous spinners for the production of articles which can be used for high temperature smelting or conversion of glass, for example mineral wool, is mentioned.

Thus, another subject of the present invention is that the flow of molten mineral is poured into the fibrous spinner, the periphery band of the fibrous spinner is drilled, through which the filament of the molten mineral escapes, and then The filament is a process for producing the mineral wool by internal centrifugation, which is attenuated to the mineral wool through the action of a gas,

The temperature of the mineral in the spinner is at least 1200 ° C. and the fibrous spinner is made of the alloy defined above.

Thus, the alloy according to the invention can fiberize glass or similar molten mineral compositions having a liquidus temperature (T _liq ) of at least about 1130 ° C., for example 1130 to 1200 ° C., in particular 1170 ° C. or more. Can be.

In general, such molten mineral compositions can be _{fibrized within} a temperature range of T _liq to T _log2.5 (for the molten composition reaching the spinner), and T _log2.5 indicates that the molten composition is 10 ^2.5 poise ( dPa.s), typically at least about 1200 ° C, for example 1240 to 1250 ° C or more.

Among such mineral compositions, it may be desirable to have a composition containing a significant amount of iron, which is less corrosive to the constituent metals of the fibrous component.

Thus, the process according to the invention advantageously uses a composition of minerals, which is particularly oxidative to chromium and capable of repairing or reconstructing the protective Cr ₂ O ₃ oxide layer produced on the surface. In this respect, essentially ferric (oxide Fe ₂ O ₃ ), in particular, the molar ratio of the II and III oxidation states expressed in the FeO / (FeO + Fe ₂ O ₃ ) ratio is about 0.1 to 0.3, in particular 0.15 to 0.20. It may be desirable to use compositions containing iron in the form.

Advantageously, the mineral composition has a high iron content such that the amount of iron oxide (the amount called "total iron" corresponding to the total iron content generally expressed in the form of equivalent Fe ₂ O ₃ ) is at least 3%, preferably Allows for a rapid reconstitution rate of chromium oxide which is at least 4%, in particular about 4-12%, in particular at least 5%. Within the redox range, the mineral composition corresponds to a content of only ferric Fe ₂ O ₃ of at least 2.7%, preferably at least 3.6%.

Such compositions are especially known from WO-99 / 56525 and advantageously comprise the following components.

SiO ₂ 38-52%, preferably 40-48%

Al ₂ O ₃ 17-23%

SiO ₂ + Al ₂ O ₃ 56-75%, preferably 62-72%

RO (CaO + MgO) 9-26%, preferably 12-25%

MgO 4-20%, preferably 7-16%

MgO / CaO ≥ 0.8, preferably ≥ 1.0 or ≥ 1.15

R ₂ O (Na ₂ O + K ₂ O) ≥2%

P ₂ O ₅ 0-5%

Total iron (Fe ₂ O ₃ ) ≥1.7%, preferably ≥2%

B ₂ O ₃ 0-5%

MnO 0-4%

TiO ₂ 0-3%

Other compositions known from WO-00 / 17117 are found to be particularly suitable for the process according to the invention.

This composition is characterized by the following weight percent content.

SiO ₂ 39-55%, preferably 40-52%

Al ₂ O ₃ 16-27%, preferably 16-25%

CaO 3-35%, preferably 10-25%

MgO 0-15%, preferably 0-10%

Na ₂ O 0-15%, preferably 6-12%

K ₂ O 0-15%, preferably 3-12%

R ₂ O (Na ₂ O + K ₂ O) 10-17%, preferably 12-17%

P ₂ O ₅ 0-3%, preferably 0-2%

Total iron (Fe ₂ O ₃ ) 0-15%, preferably 4-12%

B ₂ O ₃ 0-8%, preferably 0-4%

TiO ₂ 0-3%

MgO is 0 to 5%, in particular 0 to 2%, when R ₂ O is ≦ 13.0%.

According to one embodiment, the composition has an iron oxide content of 5-12%, in particular 5-8%. This makes it possible to have fire resistance of the mineral wool blanket.

Although the present invention has been described primarily in the context of the manufacture of mineral wool, the present invention generally produces, in particular, textile glass (yarn or strand) and packaging glass for producing components or accessories, bushings or feeders of the furnace. It can be applied to the glass industry.

Outside the glass industry, the present invention can be applied to the manufacture of a wide variety of articles, provided the articles must have high mechanical strength (especially at high temperatures) in oxidation and / or corrosion media.

In general, such alloys can be used in the chemical industry to produce any type of fixed or moving parts made of refractory alloys to operate heat exchangers or reactors with high temperature (above 1200 ° C.) heat treatment. Thus, such alloys can be used, for example, in hot fan blades, firing support, furnace-charging equipment and the like. This alloy produces any type of heat-resistant element designed to operate in hot oxidizing environments, and turbine components used in ground, marine or air transport engines, or any other device that does not include transporters, such as power plants. It can also be used to produce.

Thus, the subject of the present invention is the use of articles made of the alloys defined above in an oxidizing environment at least at 1200 ° C.

The invention is illustrated by the following examples and FIGS. 1-3 of the accompanying drawings.

1 is a phase balance diagram for one type of alloy according to the present invention.

2 is a phase balance diagram for one kind of alloy according to the present invention.

3 is a graph illustrating the comparative mechanical properties of various alloys.

First, an alloy based on cobalt reinforced by carbide containing only metal M is exemplified.

Examples 1-5 are shown in Table 1 below (content is in weight percent).

Yes Co Ni Cr C Hf Ti Zr One Base 8.7 28.4 0.4 6 - - 2 Base 8.7 28.4 0.4 3 - - 3 Base 8.7 28.4 0.4 - 1.6 - 4 Base 8.7 28.4 0.4 - 3 - 5 Base 8.7 28.4 0.4 - - 3

The microstructure of these alloys containing niobium, zirconium or hafnium carbides is visually very similar to the microstructure of similar alloys containing tantalum carbide (the comparative alloy defined above). These elements form eutectic carbides in the "script" form which favor deductively good interparticle adhesion.

When the alloys of Examples 1 and 2 are exposed to a temperature of 1200 ° C. for a long time, typically 100 hours, the microstructure remains practically undeformed, whereby the carbide can continue to act as a reinforcing agent. In addition to the stability of these microstructures, these alloys have a carbide network with a density similar to that of the comparative alloy, while introducing less carbide forming elements. In addition, a substantial increase in fire resistance is observed, in comparison with 1338 ° C. for the comparative alloy, the melting start temperature of the alloy of Example 1 is 1374 ° C. and the melting start temperature of the alloy of Example 2 is 1380 ° C.

With respect to the alloys of Examples 3 and 4 containing titanium carbide, the microstructure obtained is also satisfactory, and TiC carbide appears to be able to achieve good intergranular adhesion due to a script geometry that is entirely similar to the TaC carbide of the comparative alloy. The microstructure is less stable and highly stable in carbides than in TaC carbides of the comparative alloys in the case of Example 4, where the Ti / C atomic ratio is greater than one.

The alloy of Example 5 is also slightly smaller than the alloys of Examples 1 and 2 but is characterized by specific microstructure stability after 100 hours at 1200 ° C.

Second, an alloy based on cobalt reinforced by carbides containing titanium and tantalum at the same time is illustrated.

Phase equilibrium for the system, one of which is illustrated in FIG. 1, was determined from experimental and modeling data. This phase equilibrium represents the phase observed for a given temperature (1300 ° C. isothermal cut) as a function of titanium and tantalum mass content in an alloy based on cobalt / TaTiC (the composition of this alloy is always in percent by weight Contains the following elements: Cr = 28.34, Ni = 8.68, C = 0.4). The aim is to determine the concentration range of these two metals which gives the highest possible solidus temperature for the material. This phase equilibrium represents a very limited totally solid (matrix + TaC + TiC) range. The next example of this composition range was chosen.

Example 6

Alloys of the following composition were prepared,

Cr 28.4%

Ni 8.7%

C 0.4%

Ti 1.5%

Ta 3%

The rest of the elements are

Fe <3%

Si <1%

Mn <0.5%

Zr <0.1%

Other <1%

The rest consists of cobalt.

The thermal stability of this microstructure was demonstrated by the following treatment.

The alloy test piece was heated at a temperature of 1200 ° C. for 100 hours and then cooled in water to “cool” the microstructure.

The structure of the test piece was observed using the scanning electron microscope. This observation shows that the structure of the crystal boundary contains (Ta, Ti) C carbides dispersed in a dense network, and is also a very fine secondary (Ta, Ti) C, very useful for resistance to creep in particles. It was found that carbides precipitated in the matrix. This microstructure was not affected by exposure to high temperatures (100 hours at 1200 ° C.), and TaC carbide containing titanium was more perfectly stable than TaC carbide of alloys reinforced with tantalum carbide of the comparative example. These Ti-containing TaC carbides, which make up most of the carbides, had a microstructure that could hardly be disturbed at high temperatures, that is, there was little decomposition and coarsening of (Ta, Ti) C carbides.

The test demonstrated very high fire resistance of these carbides and their solidus temperature was in the range of 1350 ° C.

The high temperature mechanical resistance properties of the alloy were evaluated by a three point bending creep resistance test at a temperature of 1250 ° C. at 31 MPa load. This test was performed on parallelepiped specimens 30 mm wide and 3 mm thick, with a load applied in the middle between the 37 mm spaced supports. Deformation of the test piece was observed as a function of time as shown in the graph of FIG. 3. Mechanical resistance is usually expressed in creep speed.

Compared to 3.5 μm / h for the 100% TaC alloy of the comparative example, the alloy was deformed at a sag rate of 1.1 μm / h.

Oxidation resistance properties were evaluated by thermogravimetric test at 1200 ° C. Compared to 96.5 x 10 ^-12 g ² .cm ^-4 .s ^-1 for the alloy of the comparative example, a parabolic oxidation constant (K _p ) of 190 x 10 ^-12 g ² .cm ^-4 .s ^-1 was obtained. .

The oxidation action is relatively deteriorated to such an extent that it is not harmful in this temperature range, and relatively little deteriorates as compared with the alloy of the comparative example, and it is mechanical resistance to determine the quality of the material in this temperature range. Thus, the balance between these two properties is sufficiently advantageous for the alloy of Example 6 herein.

Example 7

As shown in Table 2, another alloy of the same type was prepared having a composition different from that of Example 6.

(Content in weight percent) Yes Co Ni Cr C Ti Ta 6 Remainder 8.7 28.3 0.4 1.5 3 7 Remainder 8.7 28.3 0.4 One 4

The microstructure of Example 7 is similar to the microstructure of Example 6.

The mechanical high temperature resistance properties of the alloy were evaluated in a three-point bend creep resistance test at 1250 ° C with a load of 31 MPa as before. The creep rate was 3.2 μm / h, which already showed a 10% reduction compared to the alloy of the comparative example.

The oxidation of Example 7 observed by thermogravimetry does not proceed faster than that of the comparative alloys, and the parabolic constant (K _p ) is 96.5 × 10 ^-12 g ² .cm ^-4 .s for the comparative alloys. Compared with ^-1 , it was 136 * 10 <^-12> g <^-2> cm <^-4> s <^-1> for 100 hours at 1200 degreeC.

Thermogravimetric tests performed at 1300 ° C. once again show the persistence of active oxidation through a parabolic law and a six-fold increasing constant, which is very appropriate only for test temperatures of tens of degrees below the solidus.

These alloys 6 and 7 were also tested for cyclic oxidation in air. This test consisted of 10 cycles each formed by increasing to 1200 ° C., then held for 24 hours, then air cooled, and weighing the test pieces to calculate the weight loss per unit area. Alloys 6 and 7 worked almost the same as the alloy of the comparative example.

Comparative example

The alloy of WO 01/90429 Example 1 having the following composition was reproduced.

Cr 28.3%

Ni 8.68%

C 0.37%

Ta 5.7%

W 0%

The residual element is

Fe <3%

Si <1%

Mn <0.5%

Zr <0.1%

Other <1%

The rest consists of cobalt.

The alloy is characterized in that it is reinforced with an intergranular phase consisting only of tantalum carbide.

Mechanical resistance is illustrated in FIG. 3 in which the alloy is deformed at three point creep under 31 MPa at a temperature of 1200 ° C. The action is similar to that obtained with the alloy of Example 6 (at a temperature of 1250 ° C. for Example 6).

Next, a cobalt based alloy containing both zirconium and tantalum and reinforced with carbides is illustrated.

Phase equilibrium for the system, one of which is illustrated in FIG. 2, was determined from experimental and modeling data. Phase equilibrium is an alloy based on cobalt / TaZrC for a given temperature (1300 ° C. isothermal cleavage) (this composition always contains the following elements in weight percent: Cr = 28.34, Ni = 8.68, C = 0.4) Shows the phase to be observed as a function of the mass content of tantalum and zirconium. The goal was to determine the concentration range of these two metals that gave the highest possible solidus temperature for the material. This equilibrium shows a very limited totally solid (matrix + TaC + ZrC) range. The following example was chosen from this composition range.

Examples 8-12

Tests performed on the various alloys produced (Table 3 below shows their chemical composition) show that the benefits from ZrC carbides (fire resistance and good microstructural stability) are due to TaC carbides (lower cost of production and good high temperature oxidation properties). Showed to be combined.

(Content in weight percent) Yes Co Ni Cr C Zr Ta 8 Remainder 8.7 28.4 0.4 2 2 9 Remainder 8.7 28.4 0.4 1.5 3 10 Remainder 8.7 28.4 0.4 One 4 11 Remainder 8.7 28.4 0.37 0.5 5.8 12 Remainder 8.7 28.4 0.37 0.5 5.0

The fire resistance of this alloy was tested by differential thermal analysis (DTA) to compare it with the comparative example. The melting of the alloy is generally at least 1350 ° C., in the case of the alloy of Example 8, in particular 1366 ° C., compared to 1340 ° C. for the comparative example.

The microstructure of such alloys is advantageous.

Greater structural stability of the alloy of Example 11 was noted than the comparative alloy, and carbide entanglement was observed once again after 100 hours at 1200 ° C.

For example, the alloy of Example 11 has a dense interdendritic network (guaranteed better mechanical action) of mixed ZrC-TaC carbides which are more stable and less degradable even after 100 hours at 1200 ° C. Comparative example had the same oxidation and alloys (compared to ^{96.5 × 10 -12 g 2 .cm -4} .s -1 in the case of TaC strengthened alloys, while in 1200 ℃ 10 sigan ^{_{K p = 93.6 × 10 -12 g}} 2 .cm ^-4 .s ^-1 )

Finally, cobalt based alloys containing both hafnium and tantalum and reinforced by carbides are exemplified.

Examples 13-15

(Content in weight percent) Yes Co Ni Cr Ta Hf C 13 Remainder 8.7 28.4 2 4 0.4 14 Remainder 8.7 28.4 3 3 0.4 15 Remainder 8.7 28.4 4 2 0.4

The (Hf + Ta) / C ratio of this alloy is one.

The carbide network obtained for these three alloys has an advantageous form, especially since the amount of hafnium is greater than that of tantalum.

Very good structural stability was observed for these alloys. The carbide network appeared to remain intact after 100 hours at 1200 ° C.

The fire resistance of this alloy was tested with DTA to allow comparison with the comparative example. Therefore, melting | fusing start of the alloy of Example 13 was 1382 degreeC compared with 1340 degreeC of a comparative example, and melting initiation of the alloy of Example 14 was 1366 degreeC. Thus, the fact that replacing half of tantalum with hafnium increases its melting initiation by at least 26 ° C., which is a considerable size.

The high temperature mechanical resistance characteristics of Example 14 alloy were evaluated in a three point bending creep resistance test at a temperature of 1200 ° C. under a load of 31 MPa. This result is shown in FIG.

The action of the alloy is similar to that of the comparative example in the first test section, but it can be seen that the deformation curve substantially deviates from the curve following the alloy of the comparative example.

As mentioned above, the present invention is used to produce metal alloys, which have higher mechanical strength at high temperatures, thus permitting operation at metal temperatures of 1200 ° C. or higher.

Claims (16)

As an alloy having high mechanical strength at high temperatures in an oxidation medium, In an alloy wherein the alloy does not contain molybdenum and / or tungsten and comprises a chromium containing matrix reinforced by carbide precipitation, The alloy comprises a carbide of at least one metal (M) selected from titanium, zirconium and hafnium, The carbide optionally further contains tantalum (M '). Alloy, characterized in that. The alloy of claim 1, wherein the alloy comprises a matrix based on cobalt or nickel or iron-nickel. 3. The alloy according to claim 1, wherein the alloy comprises at least 0.2% by weight, in particular at least 0.6% by weight of carbon. The alloy of claim 1, wherein the alloy comprises metal (M) and, optionally, metal (M ′), wherein the molar ratio (M + M ′) / C of metal / carbon is about 0.9. Alloy, characterized in that from 2 to 2, in particular from 0.9 to 1.5. The alloy according to any one of claims 1 to 4, wherein the alloy is essentially composed of the following elements (the ratio is expressed by weight percentage in the alloy). Cr 23 to 34% Ni 6-12% M = Zr, Hf or Ti 0.2-7% M '= Ta 0-7% C 0.2-1.2% Less than 3% Fe Si less than 1% Mn less than 0.5% The remainder consists of cobalt and inevitable impurities. 6. The alloy according to claim 1, wherein the alloy comprises 0.2 to 5 wt%, preferably about 0.4 to 5 wt% titanium. 7. 7. The alloy according to claim 1, wherein the alloy comprises 0.2 to 5 wt%, preferably about 0.4 to 3 wt% zirconium. 8. Alloy according to any one of the preceding claims, characterized in that the alloy comprises 0.2 to 7% by weight, preferably about 0.4 to 5% by weight of hafnium. 9. The alloy of claim 8, wherein the Hf / C ratio is less than one. 10. The alloy according to claim 1, wherein the tantalum content is about 1 to 7%, in particular about 2 to 6%. An article made of the alloy according to claim 1, in particular by casting, in particular an article which can be used in particular for hot smelting or converting glass. 12. The article of claim 11, wherein the article has been forged after casting. 13. The article of claim 11 or 12, consisting of a fiberizing spinner for producing the mineral wool. A method for producing an article according to any one of claims 11 to 13, Casting the molten alloy in a suitable mold. As a method of producing a mineral wool by internal centrifugation, The flow of molten mineral material is poured into the fibrous spinner, and the periphery band of the fibrous spinner is perforated so that the filament of the molten mineral material exits through the hole, and then the filament is subjected to the action of gas. In the method for producing a mineral wool by internal centrifugation, which is attenuated to the mineral wool, The temperature of the mineral material in the spinner is at least 1200 ° C., The fibrous spinner is made of the cobalt-based alloy according to any one of claims 1 to 10 Characterized in that the mineral wool by internal centrifugation. Method according to claim 15, characterized in that the molten mineral material has a liquidus temperature of at least about 1130 ° C., in particular at least 1170 ° C. 16.

Images